Electric switch contact



Oct. 1, 1940. w. F. SEUBERT 2,215,654

ELECTRIC SWITCH CONTACT Filed July 2'7. 1937 SILVER CADMIUM PLATEDCOPPER INVENTOR WILLIAM F: SEUBERT BY HIS ATTORNEYS M MWW Patented 'Oct.1 1940 UNITED STATES PATENT OFFICE ELECTRIC SWITCH CONTACT ConnecticutApplication July 27, 1937, Serial No. 156,015

7 Claims.

This invention relates to electric switch contacts. More particularly itrelates to contact members having the properties of resistance tocorrosion as well as are prevention and ex tinguishing.

It is an object of my invention to provide an electric switch contactmember which will afford maximum conductivity between the engagingsurface of cooperating contact structures and 10 will present minimumresistance to current flow through the whole contact structure,commensurate with low cost, and which will at the same time possess theproperties of arc limitation and quenching.

5 Another object is to provide a contact structure of low cost whichwill stand up under conditions of hard use while carrying its maximumrated current or-more, and will are less and show less wear from pittingand melting than other prior contact structures for similar usage.

- Other'objects and advantages of my invention will become apparent asit is described in connection with the accompanying drawing.

In the drawing the single figure shows in perspective an electric switchcontact member.

Heretofore many attempts have been made to provide electric switchcontacts which would tend to reduce the arcing and hence eliminate 'orlimit pitting, scarring and burning. In these attempts contact buttonsor engaging contact surfaces have been made of various metals andalloys, or metals plated with other metals. Most frequently copper andsilver have been used be-' cause of their known high conductivity toelectric current. In some cases these metals have been alloyed with orplated with cadmium for the purpose of reducing arcing. But in the caseof alloys the addition 'of cadmium increased the resistance as well asthe expense of the contact.

40 In the case of plated contacts the friction oi the contact surfacesin normal use caused the plating to rub off, or arcing caused it to beburned off, thus destroying the value of the plated contact. In allthese prior uses, however, the cadmium was a part of the engagingsurface, either as plating or within the alloy.

My invention avoids the defects of the prior constructions whileretaining their advantages. According to my invention a contact supportI,

of any suitable form is made of copper of as high purity as usual inelectric work, or it may be made of brass, phosphor bronze or othermaterials used for such purposes, if the size is suflicient to permitpassage of the required current without substantial loss or overheating.This support is then plated with pure cadmium, after which one or morecontact silver buttons, 2, 3 are attached to the support in any suitablemanner, as by forming the button in the shape of a rivet and upsettingthe end of it which passes through the 5 support or preferably bywelding to the support. These buttons may be made of fine silver, coinsilver, or any silver alloy having the proper degree of conductivity ofelectric current so that the buttons will not overheat nor become pittedin 10 use. The contact buttons will engage with similar fixed or movablecontact buttons on another support in the usual mariner in switches.

' It has been found by comparative tests that when the support is platedwith cadmium the 15 arcing between the stationary contacts of the switchis greatly reduced, so that whereas prior to the plating of the support,the switch might fail to perform satisfactorily on overload, it will notfail when the support is plated with cadmium. 20

Some of the outstanding advantages of m invention are 1. The cadmiumplating is not on any engaging or contact surface and hence it will notrub off nor is it likely to be burned off. 25

2. The contact buttons may be made of the best conducting materialatpresent known, 1. e., silver, or of any metal or alloy of high currentconductivity.

3. The support may be made of the best and 30 most commonly usedmaterial for ordinary current conduction in electric work, i. e.,copper, or of any suitable conductive material of lower cost than thecontact buttons.

4. The use of the materials in the manner de- 35 scribed results in lessarcing than any other prior construction having as simple structure andas low relative cost.

I have found that superior results are also obtained when the plating isof aluminum instead 40 of cadmium. The aluminum proved to have theproperties of arc quenching or reduction similar to cadmium.

I have also found that good results may be obtained when the plating isof zinc instead of 5 cadmium, though the arc reduction and quenchingproperties of cadmium and aluminum are superior to zinc, as usedaccording to the principles of my invention. Therefore, I do not limitmyselfto the specific form of the contact member 50 as described but,

I claim- 1. An electric switch contact member comprising a supportingmember of copper, a silver contact button mounted on said support andform- 55 ing the contact surface of said contact member, and a platingof cadmium on said support at least on the area around said button.

2. An electric switch contact member comprising a supporting member ofmaterial having high electric conductivity, and a contact button mountedon said support and forming the contacting surface of said contactmember, a plating of cadmium on said support at least on the area aroundsaid button, said button being of metal having high electricconductivity and high resistance to pitting or welding.

3. An electric switch contact member comprising a supporting member ofmaterial having high electric conductivity, contact buttons mounted onsaid support and forming the contacting surface of said contact member,a plating of cadmium on said support at least on the area aroundsaidbutton, said button being of the class of metals including silver andits alloys which possess high electric conductivity and resistance topitting or welding.

4. An electric switch contact member comprising a supporting member ofcopper, at contact button mounted on said support and forming thecontacting surface of said contact member, a plating of cadmium on saidsupport at least on the area around said button, said button being ofthe class of metals including silver and its alloys which possess highelectric conductivity and resistance to pitting or welding.

5. An electric switch contact member having a support whose area aroundthe contacting surface is plated with cadmium, said area being free ofengagement with any other contact member in normal use.

6. An electric switch contact member having a conducting support, acontact button of material having good electric conductivity, and aplating of material having property of arc reduction or quenching onsaid support on the area around said button.

7. An electric switch contact member having a support whose area aroundthe contacting sur- ,4

face is plated with aluminum, said area being free of engagement withany other contact member in normal use.

WILLIAM F. SEUBERT.

